A secondary battery is known, with electrodes made of reversible electrochemically doped, conjugated polymers, from European patent application No. EP-A-0036118. The electrodes described therein are made especially of a doped polyacetylene, with the electrolyte containing an ionizable compound in which anionic and cationic dopants for the electrodes can be used. The use of polyacetylene as an electrode material has the disadvantage of being relatively expensive and that it inhibits a low electrical conductivity in its undoped state. Furthermore, it is relatively sensitive to water and oxygen. This results in handling difficulties of polyacetylene, which together with the required encapsulation of electrode elements made from it, makes such units relatively expensive.
It is an object of the present invention to provide a storage element for electrical energy which will have improved life expectancy and improved electrical performance, as well as lower costs.